Subterranean termites enter a wooden structure through holes and cracks in foundations and walls. The art is replete with techniques to prevent their entry. Metal flashings, concrete stem walls that rise above grade, and sealants to close holes and cracks are widely-encountered examples.
The better known techniques are not usually long-lived. Foundations, for example, can and do crack, enabling the termites to enter the structure. Heaving of the ground or growth of roots often create voids through which the termites pass. There remains a need for an inexpensive, easily installed barrier which can withstand disruptive forces, discourage the entry of roots through it, and prevent the passage of termites.
It is known that termites cannot pass through barriers of sand whose particles are of certain sizes. It appears that some sizes are too large to be moved aside by the termites or seized by their mandibles and carried away, and that certain sizes are not so large as to leave spaces through which the termites can pass. This type of barrier is disclosed in Journal of Economic Entomology Vol. 50, No. 5, pp 690-692 Oct. 1957 by Walter Ebeling and Roy J. Pence. The first-named author in this article is one of the applicants in the instant patent application.
The extermination industry has long relied on insecticides applied as sprays or streams. These are very cost effective, and over the years have not caused much objection. However, as awareness has grown about the potentially harmful effects of insecticides, resistance has arisen to their continued use, especially by chemically-sensitive persons.
In view of this increased awareness, it is surprising that with the advantages offered by the process described in the article, there has been no commercial use made of this technique, at least to the knowledge of the present applicants. Upon relfection, the applicants have concluded that it has suffered fromlack of a simple method of application, and also from means to keep the barrier in place and in conformity with adjacent structures once it is applied. If it washes away, or ultimately cracks or fails to conform to the structure it protects, then its protective value is lost.
It is an object of this invention to provide a conveniently installed barrier to passage of termites, and methods and constructions which assure its long-lived effectiveness.